I had originally planned on racking a new brew right on top of the yeast cake from a batch I racked over to a secondary. After racking there just too much junk stuck to the sides of the carboy so I just harvested about 2 quarts of the slurry which is in a growler, lid on, in the refrigerator. Didn't get to brew today and apparently there is some unwritten rule that says my kids and I can't brew on Mother's Day. Who knew? Anyway, so we're going to brew on Monday.

I read somewhere at some point that you can just pitch a cup of that slurry and it will be just fine for a 5 gal batch. This is WLP001 yeast I harvested, and the Ale I'm brewing should have an O.G. of 1.068. So I don't think that 1 Cup of slurry is going to be enough. Since I have an extra day I was thinking I could take that cup to make a starter. Or should I just use the 2 quarts in it's entirety.

The way I see it if I can make a large enough starter from a portion of what I have now, I can save the rest for the next batch. Just dumping the whole thing would certainly be easier though.

You can repitch the yeast, using the MrMalty Yeast Pitching Calculator to determine how much you need to pitch (it might help to know that there are 237 mL in a cup).

You can re-pitch using the method I use, which is based on the concept that you want 2-3 doublings of the yeast in a batch of ale. If you take a yeast cake and re-pitch into an identically sized batch, that would mean 1/8-1/4 of the yeast cake is appropriate. Since I usually re-pitch after the yeast has been in the fridge for a week, I tend toward the high end to correct for loss of viability. If the beer is larger, you can increase the amount proportionately.

In either case, you should be able to have plenty to pitch and enough left over for your next batch.

You can also make a starter, if you want. I don't think you need to, since you have plenty of yeast and it is quite fresh, but a starter is probably never a bad idea.

I checked Mr Malty and it says I needed about a half cup of slurry if pitched directly. I'd rather be safe than sorry so I used the half cup but made a starter for it anyway. boiled 1 cup light DME and 4 cups of water. Vigorous shaking to aerate in a Growler, added teaspoon of yeast nutrients and pitched the slurry, capped with an airlock, wrapped in towel. Will decanter off the liquid and pitch the happy results tomorrow.

Now I still have a great deal of slurry to deal with. Should I leave it in the Growler in the refrigerator? How long will it keep? I have some pint (1/2 cup) mason jars would it be better to store the slurry in those to use as needed rather than exposing the whole batch each time I want to use it?

Way too big of a starter when using fresh slurry. kräusen over the top of the growler. would have been a huge mess if I didn't have it wrapped in a towel. Now wondering if I should pitch the whole thing or still try to poor off the liquid. How much suspended yeast will I lose.

In that short a time frame, I think you'll need to pitch the whole starter.

The yeast cake will keep best if you minimize the oxygen exposure. I store it in mason jars and keep it as cold as possible without freezing. In that case, it should have very good viability for a couple weeks, but will probably about have half as many living cells by 1 month.

Should have checked this thread again before brewing today. Did another starter from the slurry from the same batch. this time I used 1/2 cup of slurry, 1/2 cup of DME, little yeast nutrient and 2 cups of water. But, I just made the starter yesterday. How long should I allow when making a starter before brewing?

With a half-cup starter, you are mostly just waking up the yeast and, with such little volume, you can just pitch the whole thing while it is active. That probably means that you can make it the day before.

Usually, you want to grow yeast during a starter, which can mean from 1 quart to gallons of starter. In those cases, you are pushing how much starter wort you want to pitch into your beer, so it's good to start it 3 or,preferably, more days in advance. Then you can give it a day or two to actively ferment, then move to the fridge to drop the yeast out, so you can decant the starter wort and pitch mostly just the yeast.